Power Tools: map, filter & Comprehensions
9 min · Python
Python's shortcuts for transforming and filtering a list in one line.
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By now you've written plenty of loops that build a new list by starting with an empty one and calling .append() inside a for loop. That pattern is so common in Python that the language has a dedicated shorthand for it: the list comprehension.
A list comprehension builds a new list in a single line: [expression for item in iterable]. It reads almost like a sentence — "give me expression, for every item in iterable" — and produces exactly the same result as the equivalent multi-line for loop with .append(), just more compactly and, once you're used to reading it, more clearly.
Run this to build a list of squares without writing out the loop.
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